Celtics Coach Brad Stevens said of the Philadelphia 76ers, Boston’s opponent in the first-round of the playoffs, “they (have) a lot of good basketball players.” Mike Ehrmann/Pool Photo via the Associated Press

KISSIMMEE, Fla. — Some critics think the Philadelphia 76ers are in trouble without Ben Simmons.

Boston Coach Brad Stevens is not among them. His third-seeded Celtics will face the sixth-seeded Sixers in the opening round of the Eastern Conference playoffs. Game 1 is scheduled for 6:30 p.m. Monday.

The Celtics have paid attention to the Sixers, realizing they would be a likely opponent.

“They are a heck of a team,” Stevens said Thursday following a 96-90 loss to the Washington Wizards in Boston’s regular-season finale. “The games that Simmons hasn’t played, they’re the No. 1 offense in the league.”

Stevens has noticed the solid spacing and shooting around Joel Embiid while he’s posting up. Stevens also noted the Sixers’ ability to play big with both Embiid and Al Horford, or to go small with Embiid or Horford at center surrounded by shooters, and said it makes the Sixers “very tough.”

“Super physical, well-coached, good basketball team,” Stevens said. “Obviously, everybody talks about their front court, rightfully so, in Tobias Harris, Horford and Embiid.

“But they (have) a lot of good basketball players.”

The same can be said about the Celtics (48-24). Boston had a four-game winning streak before the loss against the Wizards (25-47) – a game in which the Celtics rested Jayson Tatum, Kemba Walker, Jaylen Brown, Gordon Hayward, Daniel Theis and Marcus Smart.

The victory enabled the Wizards to avoid finishing 0-8 in seeding games.

After taking Friday off, the Celtics will spend the next couple days preparing for the Sixers (42-30).

Some may say the Sixers have an advantage after winning three of this season’s four regular-season games. Philadelphia prevailed by an average of 10.3 points in the first three before suffering a 116-95 road loss on Feb. 1.

Embiid had the second-worst shooting performance of his NBA career in the loss, making only 1 of 11 shots while finishing with 11 points. That kept the Sixers from sweeping their longtime Atlantic Division rival in a season series for the first time since 2000-01.

“We know that they are going to come out hard,” Semi Ojeleye said of the Sixers. “Like I said, they are a great team. We have to make sure that we are emotionally ready to compete, and from there, everything else will take care of itself.”

The teams will meet in the playoffs for the second time in three seasons and for the 22nd time dating back to when the Sixers were the Syracuse Nationals.

Boston has won the last four playoff matchups, and 13 total.